Multi-stage polymeric latexes, coating compositions containing such latexes, and articles coated therewith

Abstract

An aqueous coating composition is provided that is useful in coating a variety of substrates, including interior or exterior portions of food or beverage cans. The coating composition includes a resin system that includes a multi-stage latex. In some embodiments, the multi-stage latex is formed using a process that includes emulsion polymerizing two or more stages in the presence of an aqueous dispersion including a water-dispersible polymer. In certain preferred embodiments, the water-dispersible polymer is a polyether polymer.

1 - 44 . (canceled) 
     
     
         45 . An aqueous interior food or beverage container coating composition comprising a multi-stage polymeric latex comprising two or more emulsion polymerized stages, wherein the two or more stages are emulsion polymerized in the presence of an aqueous dispersion of a water-dispersible polymer comprising a polyether polymer, and wherein the latex has one or both of:
 (i) a lower Tg emulsion polymerized stage having a calculated Tg that is at least 20° C. lower than a calculated Tg of a higher Tg emulsion polymerized stage, or   (ii) a gradient Tg with at least a 20° C. differential in the calculated Tg of monomers fed at the start of polymerization compared to monomers fed at the end of polymerization; and   
       wherein the coating composition is not prepared using halogenated monomers and is substantially free of each of bisphenol A, bisphenol F, and bisphenol S. 
     
     
         46 . The coating composition of  claim 45 , wherein the water-dispersible polymer comprises a polyether-acrylate copolymer. 
     
     
         47 . The coating composition of  claim 45 , wherein the polyether polymer is formed from reactants including (i) an extender and (ii) a diepoxide of an aromatic diol, aromatic diacid, aliphatic diol, aliphatic diacid, cycloaliphatic diol, cycloaliphatic diacid or combination thereof. 
     
     
         48 . The coating composition of  claim 45 , wherein the polyether polymer is formed from reactants including an extender and a diepoxide of an aromatic diol. 
     
     
         49 . The coating composition of  claim 48 , wherein the polyether polymer is formed from reactants including an extender and a diepoxide of an ortho-substituted dihydric phenol. 
     
     
         50 . The coating composition of  claim 48 , wherein the aromatic diol comprises 4,4′-methylenebis(2,6-dimethylphenol). 
     
     
         51 . The coating composition of  claim 47 , wherein the extender comprises hydroquinone. 
     
     
         52 . The coating composition of  claim 49 , wherein the extender comprises hydroquinone. 
     
     
         53 . The coating composition of  claim 45 , wherein the water-dispersible polymer has an acid number from 40 to 200 mg KOH per gram. 
     
     
         54 . The coating composition of  claim 45 , wherein the weight ratio of water-dispersible polymer to emulsion polymerized stages is less than 40:60. 
     
     
         55 . The coating composition of  claim 45 , wherein the latex has a lower Tg emulsion polymerized stage having a calculated Tg of less than 30° C. and a higher Tg emulsion polymerized stage having a calculated Tg of greater than 50° C. 
     
     
         56 . The coating composition of  claim 55 , wherein the latex has a lower Tg emulsion polymerized stage having a calculated Tg that is at least 40° C. lower than a calculated Tg of the higher Tg emulsion polymerized stage. 
     
     
         57 . The coating composition of  claim 54 , wherein more than 50 weight percent of the emulsion polymerized stages have a calculated Tg of at least 40° C. 
     
     
         58 . The coating composition of  claim 45  wherein the coating composition includes, based on total resin solids, at least 50 wt. % of the two or more emulsion polymerized stages. 
     
     
         59 . The coating composition of  claim 45 , wherein the coating composition contains more than 70 wt. % resin solids from polymerized ethylenically unsaturated monomers based on total resin solids in the coating composition. 
     
     
         60 . The coating composition of  claim 58 , wherein the coating composition comprises a beverage inside spray coating composition that, when spray applied onto an interior of a 355 mL no. 211 two-piece drawn and ironed aluminum beverage can at 115 milligrams per can coating weight and cured at 188° C. to 199° C. (measured at the can dome) for 55 seconds, exhibits:
 (i) a global extraction result of less than 50 ppm; 
 (ii) a metal exposure of less than 3 mA on average when the can is filled with 1% NaCl in deionized water and tested pursuant to the Initial Metal Exposure test method disclosed herein; and 
 (iii) gives a metal exposure of less than 3.5 mA when tested pursuant to the Metal Exposure after Drop Damage test disclosed herein. 
 
     
     
         61 . The coating composition of  claim 60 , wherein at least one of the emulsion polymerized stages is formed from monomers including at least 80 wt. % of one or more of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate. 
     
     
         62 . The coating composition of  claim 45 , wherein the coating does not contain any structural units derived from a bisphenol. 
     
     
         63 . The coating composition of  claim 45 , wherein coating composition further comprises a phenoplast crosslinker. 
     
     
         64 . An aqueous interior food or beverage container coating composition comprising a multi-stage polymeric latex that is not prepared using halogenated monomers and comprises two or more emulsion polymerized stages at least one of which is formed from monomers including at least 50 wt. % of one or more (meth)acrylates, wherein the two or more stages are emulsion polymerized in the presence of an aqueous dispersion of a water-dispersible polymer comprising a polyether polymer, and wherein:
 the latex has a lower Tg emulsion polymerized stage having a calculated Tg that is at least 40° C. lower than a calculated Tg of a higher Tg emulsion polymerized stage,   the polyether polymer is formed from reactants including (i) an extender and (ii) a diepoxide of an aromatic diol, cycloaliphatic diol, or combination thereof, and   the coating composition is substantially free of each of bisphenol A, bisphenol F, and bisphenol S; and   the coating composition is an inside spray beverage can coating composition that, when spray applied onto an interior of a 355 mL no. 211 two-piece drawn and ironed aluminum beverage can at 115 milligrams per can coating weight and cured at 188° C. to 199° C. (measured at the can dome) for 55 seconds, exhibits:
 (i) a global extraction result of less than 50 ppm; and 
 (ii) a metal exposure of less than 3 mA on average when the can is filled with 1% NaCl in deionized water and tested pursuant to the Initial Metal Exposure test method disclosed herein. 
   
     
     
         65 . The coating composition of  claim 64 , wherein the water-dispersible polymer has an acid number from 40 to 200 mg KOH per gram, and wherein the weight ratio of water-dispersible polymer to emulsion polymerized stages is less than 40:60. 
     
     
         66 . The coating composition of  claim 65 , wherein the coating composition is substantially free of styrene, and wherein the coating composition includes or is derived from no more than 0.5 wt. % of acrylamide-type monomers based on the aggregate weight of the ethylenically unsaturated monomer component and polymerizable monomers employed to make the latex. 
     
     
         67 . The coating composition of  claim 65 , wherein the coating composition, when spray applied onto an interior of a 355 mL no. 211 two-piece drawn and ironed aluminum beverage can at 115 milligrams per can coating weight and cured at 188° C. to 199° C. (measured at the can dome) for 55 seconds, is capable of passing a necking and flanging test as indicated by a change of metal exposure after necking of less than 1.0 mA. 
     
     
         68 . The coating composition of  claim 64 , wherein the water-dispersible polymer comprises a polyether-acrylate copolymer, and wherein the polyether polymer is formed from reactants including (i) an extender and (ii) a diepoxide of an aromatic diol, cycloaliphatic diol, or combination thereof. 
     
     
         69 . The coating composition of  claim 68 , wherein the coating does not contain any structural units derived from a bisphenol. 
     
     
         70 . The coating composition of  claim 64 , wherein coating composition further comprises a phenoplast crosslinker.